Flowers at Zion 3: The Little Yellow Flower

Little Yellow Flowers are like Little Gray Birds.
There are a lot of them,
and without my book in hand I simply cannot recall which is which.
Fortunately I remembered to take multiple views--
not just details of the blooms,
but of the leaves, and whole plant,
and scale views with my fingertip.
So, these specimens are (top to bottom):

Baileya multiradiata (desert marigold),
Chrysopsis villosa (hairy goldenaster),
Melilotus officinalis (yellow sweet clover)
-- and this stuff was everywhere--
and finally, in only one spot,
Cylindropuntia (species?- a cholla.)
I think the cholla got planted as an ornamental, on purpose,
because it was near a building structure.